A crotofolane-type diterpenoid and a rearranged nor-crotofolane-type diterpenoid with a new skeleton from the stems of Croton cascarilloides

From the stems of Croton cascarilloides collected in the Okinawa Islands, a structurally rare crotofolane-type diterpenoid (1) and a rearranged nor-crotofalane, a new skeletal diterpenoid (2), were isolated. The structures were determined by X-ray crystallographic analyses, establishing their absolute stereostructures for the first time. Compound 2 was probably biosynthesized from 1 through several steps, such as decarboxylation, oxidation, C-C bond migration, etc.